As for an exhaust apparatus of an internal combustion engine, in order to minimize emission of HC, NOx or the like by rapid activation of catalyst, when the engine is cold, i.e., in a warm-up period immediately after the engine was started, there is known heretofore such an apparatus that is provided with a start catalytic converter (pre-converter) served as an exhaust processing device, on a main flow passage immediately below an exhaust manifold. Also, the apparatus is provided with a bypass flow passage to detour the device after the warm-up of the engine, and provided with a valve mechanism for switching those flow passages. For example, Patent document 1 proposes such an apparatus that is provided with a catalyst valve for limiting inflow of exhaust into the start catalytic converter (pre-converter) served as the exhaust processing device, and provided with a bypass valve for limiting the inflow of exhaust into the bypass flow passage, to regulate exhaust pressure in response to operating conditions, with those valves being opened or closed independently.
It is concretely described that two valves of the catalyst valve and bypass valve are provided, and that an electromagnetic actuator for opening or closing the catalyst valve, and a diaphragm actuator for opening or closing the bypass valve are controlled independently in response to the operating conditions, as follows: That is, when a heavy load is applied to the internal combustion engine (after the warm-up), the catalyst valve is placed in its closed position, and the bypass valve is placed in its opened position. On the contrary, when the engine is cold (warming-up period), the bypass valve is placed in its closed position, and opening range of the catalyst valve is controlled by its duty. And, when the engine is started, the catalyst valve is placed in its fully opened position, and the bypass valve is placed in its closed position. Furthermore, when a middle or light load is applied after the warm-up, the catalyst valve is placed in its fully opened position, and the bypass valve is placed in its closed position.
Also, Patent document 2 describes, with respect to an exhaust gas recirculation device (EGR) for circulating a part of the exhaust gas of the internal combustion engine into an intake passage, such prior arts as a technology of realizing an internal EGR by a valve timing variable mechanism, and a technology for increasing the exhaust pressure by throttling the exhaust flow rate to activate the catalyst rapidly, and proposes such a device that is aimed to obtain both of the output and the EGR amount on a high level, and discloses the structure with a throttle valve disposed on the downstream side of the catalytic converter.
On the other hand, Patent document 3 discloses an exhaust noise reducing apparatus, which is provided with a bypass passage in an exhaust pipe on the upstream side of a catalyst, and a switching valve in its inlet portion. Also, in Patent document 4, there is proposed an apparatus for reducing exhaust noise, which is provided with bypass exhaust gas volume control means for controlling the bypassed exhaust gas volume in response to exhaust gas temperature, and provided with a volume section having a predetermined capacity. Furthermore, in Patent document 5, there is proposed an apparatus for suppressing deterioration of catalyst, to ensure engine brake by employing such a structure that prohibits a fuel-cut, and throttle an exhaust path according to predetermined conditions.
In the mean time, as for the exhaust processing device, such devices as an exhaust heat recovery device and a heat exchanging device are included, in addition to the catalytic converter or the like as described above. According to those devices, the exhaust process such as heat recovery or heat exchange to the exhaust gas is made according to requirements, which are included in the exhaust processing requirements, together with the exhaust purifying requirements as described before. For example, in Patent document 6, there is proposed an exhaust heat recovery device for an engine, which is aimed to increase exhaust heat quantity by actively promoting heat generation in the catalytic converter, and which is provided with an exhaust heat exchanger for exchanging heat between a heat transfer medium and the exhaust passed through the catalytic converter. And, as its practical structure, it is so constituted that bypass channels are formed in the exhaust heat exchanger, and that the channels are switched by three exhaust channel switching valves. Also, in Patent document 7, there is proposed a heat recovery device for an internal combustion engine, which recovers heat energy at a high efficiency, without causing reduction in power of the internal combustion engine. And, FIG. 8 of it shows an embodiment, which is provided with a valve in a flow passage for bypassing a heat exchange section. It is described that in the case where the exhaust gas is equal to or smaller than a predetermined flow rate, the valve is activated to be closed by biasing means, and that in the case where the exhaust gas has increased to exceed the predetermined flow rate, the valve is opened to provide an opening area determined in proportion to the exhaust gas flow rate.
On the other hand, in Patent document 8, it is pointed out that an exhaust passage is to be throttled by means of an exhaust control valve for controlling inflow of the exhaust gas into an exhaust manifold, in order to increase back pressure of an internal combustion engine, and there is proposed an exhaust apparatus for the internal combustion engine, which is capable of performing various controls by a single exhaust control valve. The apparatus is provided with the exhaust control valve and at least a pair of exhaust gas outlet ports, on the outlet of the exhaust passage connected to an exhaust port of the engine, and the exhaust control valve can be controlled to be placed in at least three positions, i.e., a position where the exhaust gas flowing from the outlet of the exhaust passage is fed into one exhaust gas outlet port, a position where the exhaust gas flowing from the outlet of the exhaust passage is fed into the other exhaust gas outlet port, and a position where the outlet of the exhaust passage is almost fully closed.
Patent Document 1:
    Japanese Patent Laid-open Publication No. 9-125940Patent Document 2:    Japanese Patent Laid-open Publication No. 2003-83142Patent Document 3:    Japanese Patent Laid-open Publication No. 2002-303164Patent Document 4:    Japanese Patent Laid-open Publication No. 9-88568Patent Document 5:    Japanese Patent Laid-open Publication No. 2002-256863Patent Document 6:    Japanese Patent Laid-open Publication No. 2004-169594Patent Document 7:    Japanese Patent Laid-open Publication No. 2000-64833Patent Document 8:    Japanese Patent Laid-open Publication No. 2001-12260